Regarding the 4 conical white "thingys",---??? No clue. (A somewhat unique way of attaching them to the posts.)

The platform with rail, steps with rail and the ladder seem to indicate some equipment or apparatus might have located on or carried to the platform and/or that required routine attention. It might have related to ship navigation in the Mouth of Shannon, the River Shannon being a significant commercial waterway. This site was once a Loran-C station and presently a DGPS transmitter station. Concerning the curved rods or supports some of the other Irish lights have similar.

The 4 cones are probably antennas for the GPS system I would think. Thanks for the info and the larger photos. We hams have an antenna system called a four square which is similar to what is on the top of that lighthouse but usually much larger for the lower HF bands eg 80 meters. That little array on the lighthouse would be for UHF or higher frequencies probably in the microwave band.

It's interesting the uses that some lighthouses are put to. We have one here at Point Lonsdale which serve as a lighthouse but also a comms shack for the pilots controlling entry and exit into Port Phillip bay. It's a mass of antennas:-

Thanks Dave. It operates on 1.575GHZ at the upper end of the UHF band according to the FCC spectrum allocation guide:-http://www.jneuhaus.com/fccindex/960_mhz.html"Airborne electronic aids to navigation and associated land stations [Part 87 Subpart Q]

1575.42 MHz GLOBAL POSITIONING SYSTEM"

A lighthouse is probably a logical place to put something like that providing it's secure from vandals.